<h2>DESCRIPTION</h2>

A rhumbline (loxodrome) is a line following a constant angle of the
compass (i.e., a line of constant direction). It crosses all meridians
at the same angle, i.e. a path of constant bearing.

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<em>d.rhumbline</em> displays the
rhumbline joining any two user-specified points in the
active frame on the user's graphics monitor.  The named
coordinate locations must fall within the boundaries of the
user's current geographic region.

<p>The user has to specify the starting and ending
longitude/latitude coordinates of the rhumbline and
(optionally) the color in which the rhumbline will be
displayed; in this case, the program will run
non-interactively.

<h2>EXAMPLE</h2>

A geodesic line if shown over the political map of the world
(demolocation dataset):

<div class="code"><pre>
g.region vector=country_boundaries -p
d.mon wx0
d.vect country_boundaries type=area
d.rhumbline coordinates=55:58W,33:18S,26:43E,60:37N \
  line_color=yellow
# show additionally 10 degree grid
d.grid 10
</pre></div>

<p><center>
<img src="d_rhumbline.png" border=1><br>
<i>Rhumbline (loxodrome)</i>
</center>

<h2>NOTES</h2>

This program works only in GRASS locations with longitude/latitude 
coordinate system. 

<h2>SEE ALSO</h2>

<em>
<a href="d.geodesic.html">d.geodesic</a>,
<a href="d.grid.html">d.grid</a>,
<a href="m.measure.html">m.measure</a>
</em>

<h2>AUTHOR</h2>

Michael Shapiro, U.S. Army Construction Engineering Research Laboratory

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